The invention relates to wireless local area networks (WLAN), and more particularly to a background scan mechanism for a mobile station in a WLAN.
This section is intended to introduce the reader to various aspects of the art, which may be related to various aspects of the invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of related art.
According to a conventional handover mechanism, a handover operation is initiated by a mobile station (MS), such as a mobile phone, rather than an access point (AP). The mobile station performs a background scan to gather information to determine a time and target for the handover operation.
Conventionally, background scans and other applications may interfere with each other. For example, according to a real-time transport protocol (RTP), a RTP packet can carry any data with real-time characteristics, such as interactive audio and video. Referring to FIG. 1A, a RTP packet 10 is sent at intervals of T. For example, for VoIP (Voice over IP) data, T may be 20 ms (G.711 and G.729) or 30 (G. 723.1); for IPTV data, T may be at least 20 ms (AMR and AWB). For example, in a wireless network system comprising 14 WLAN channels, it takes 14 S to complete a round of background scan, wherein S is the time required for scanning one channel. Generally, S ranges between 7 ms and 11 ms. Accordingly, it takes 154 ms (11*14) to complete a round of background scan. In this case, if the priority is given to RTP packets 10, operations of background scan 13 may be interrupted by delivery of a RTP packet 10, as shown in FIG. 1B. On the other hand, if the priority is given to the background scan 13, delivery of the RTP packet 10 may be blocked by the background scan 13, as shown in FIG. 1C.
Therefore, a background scan mechanism is required to perform the background scan without interfering with other delivery operations.